debug.setproto Synchronous

Replace one nested prototype reference in a Luau function. It affects closures created from that nested slot after the change, so retain a matching original closure if you plan to restore it.

Syntax

Luau

debug.setproto(target: Function | number, index: number, replacement: Function) -> ()

Parameters

Function parameters
Parameter	Type	Description
`target`	`Function \| number`	Luau function or visible stack level containing the nested prototype.
`index`	`number`	One-based child prototype slot.
`replacement`	`Function`	Luau function with the required upvalue count.

Returns

()

No value.

Usage notes

Replacement upvalue count must match the target prototype’s upvalue count.

Example

Luau

local function factory() return function() return "before" end end
local original = factory()
debug.setproto(factory, 1, function() return "after" end)
print(factory()()) -- after
debug.setproto(factory, 1, original)